Four-color flow cytometric analysis of myeloma plasma cells

Malignant plasmacytes in bone marrow detected by flow cytometry as a predictor for the risk stratification system of multiple myeloma

BACKGROUND

Multiple myeloma (MM) is a clonal disorder characterized by the proliferation of plasma cells and their accumulation within the bone marrow (BM). The flow cytometric analysis is an essential method for the hematological diseases because of high sensitivity.

AIMS

This study evaluates the indication role of malignant plasmacytes (PCs) in BM detected by flow cytometry for the risk stratification of MM.

METHODS

Whole BM samples from 92 newly diagnosed MM patients were included in the study. We collected 10⁶ cells each sample by flow cytometry. Then we analyzed the correlation between the malignant PCs in BM and the characteristics of patients.

RESULTS

In this study, patients were stratified according to different baseline characteristics and the median ratio of the malignant PCs were compared. The significant statistical differences (p < 0.05) were: Hb < 100 g/L versus ≥100 g/L; β2-microglobulin <3.5 mg/dL versus 3.5-5.5 mg/dL versus >5.5 mg/dL; LDH > 250 U/L versus LDH 250 U/L; ISS I versus ISS II versus ISS III; R-ISS I versus II versus III. The detailed data are showed in Table 2. The significant correlations were observed between the malignant PCs in BM and (Figure 1): plasma cell of biopsy, hemoglobin, β2-microglobulin, lactate dehydrogenase (LDH), creatinine. "Double hit" or "triple hit" are defined as containing any two or three of the high risk cytogenetic abnormalities (t(4;14), t(14;16), t(14;20); del17q; TP53 mutation; 1q21 gain) by mSMAR. "Double or triple hit" had independently unfavorable significance for overall survival. As expected, the malignant PCs of "double or triple hit" group is significantly higher than the group B (one high risk genetic factor) and the group A (normal cytogenetic) (p < 0.0001 and p < 0.019).

CONCLUSION

Multiparametric flow cytometry is a highly sensitive method to identify and quantify malignant PCs. And the ratio of malignant PCs detected by MFC showed strongly correlation with the severity of the pathology of MM. Malignant PCs in BM detected by flow cytometry could be regarded as a predictor for the risk stratification system of MM. Thus, it should be considered applying in the routine evaluation of MM at diagnosis and after therapy.

Flow Cytometric Evaluation of Traditional and Novel Surface Markers for the Diagnosis of Plasma Cell Dyscrasias

Increasing interest has been expressed for flow cytometric immunophenotyping for diagnosis and monitoring in plasma cell dyscrasias over the last decades. The aim of this investigation was to compare the expression strength of various cell surface markers used traditionally or currently under investigation on normal and abnormal PC populations. We enrolled 295 consecutive patients undergoing bone marrow aspiration in the workup of monoclonal gammopathies, selecting 54 normal and 241 abnormal PC populations via flow cytometry to characterize the expression of CD45, CD38, CD138, CD19, CD56, CD20, CD27, CD28, CD81, CD117 and CD200 on the cell surface of PCs. We observed significant differences in the expression strength of all assessed markers between normal and abnormal PC populations in all markers except for CD20. While none of them was conclusive on its own, the combination of CD81 positivity and CD117 negativity was present in 98.1% of normal PC populations tested. In contrast, particularly CD117 positivity, but also CD81 negativity was indicative of an abnormal PC phenotype. Our results highlight the descriptive value of CD81 and CD117 for the allocation of bone marrow PCs to a normal or abnormal phenotype.

Combination of t(4;14), del(17p13), del(1p32) and 1q21 gain FISH probes identifies clonal heterogeneity and enhances the detection of adverse cytogenetic profiles in 233 newly diagnosed multiple myeloma

Background

Our aim was to set the FISH combination of del(17p13), t(4;14), 1q21 gain and del(1p32), four adverse cytogenetic factors rarely evaluated together, and compare our technical thresholds with those defined in the literature.

Methods

Two hundred thirty-three patients with MM at diagnosis were studied using FISH to target 4 unfavorable cytogenetic abnormalities: 17p13 deletion, t(4;14) translocation, 1p32 deletion and 1q21 gain. Technical thresholds were determined for each probe using isolated CD138-expressing PC from patients without MM.

Results

The FISH analysis identified abnormalities in 79.0% of patients. Del(17p13) was detected in 15.0% of cases, t(4;14) in 11.5%, 1q21 gain in 37.8% and del(1p32) in 8.7%. Adding 1p32/1q21 FISH probes has enabled us to identify adverse cytogenetic profiles in 39.0% of patients without del(17p13) or t(4;14). Clonal heterogeneity was observed in 51.1% of patients as well as an increase in the number of adverse abnormalities when related clones were greater than or equal to 2 (85.1% against 45.6%).

Conclusion

FISH allowed detecting accumulation of adverse abnormalities and clonal heterogeneity in MM with a combination of 4 probes. The impacts of these two parameters need to be evaluated, and could be included in future cytogenetic classifications.

Immune defects in the risk of infection and response to vaccination in monoclonal gammopathy of undetermined significance and multiple myeloma

The plasma cell proliferative disorders monoclonal gammopathy of undetermined significance (MGUS) and malignant multiple myeloma (MM) are characterized by an accumulation of transformed clonal plasma cells in the bone marrow and production of monoclonal immunoglobulin. They typically affect an older population, with median age of diagnosis of approximately 70 years. In both disorders, there is an increased risk of infection due to the immunosuppressive effects of disease and conjointly of therapy in MM, and response to vaccination to counter infection is compromised. The underlying factors in a weakened immune response in MGUS and MM are as yet not fully understood. A confounding factor is the onset of normal aging, which quantitatively and qualitatively hampers humoral immunity to affect response to infection and vaccination. In this review, we examine the status of immune alterations in MGUS and MM and set these against normal aging immune responses. We focus primarily on quantitative and functional aspects of B-cell immunity. Furthermore, we review the current knowledge relating to susceptibility to infectious disease in MGUS and MM, and how efficacy of conventional vaccination is affected by proliferative disease-related and therapy-related factors.

Utility of a column-free cell sorting system for separation of plasma cells in multiple myeloma FISH testing in clinical laboratories

Targeted FISH analysis is an essential component of the management of plasma cell myeloma for identification of cytogenetic abnormalities. The purpose of this study was to evaluate the column-free method, RoboSep® (RS), for sorting CD138-expressing cells in bone marrow aspirates. Comparative analysis of column-based and RS methodologies was carried out on 54 paired bone marrow aspirate validation samples from patients undergoing work-up for plasma cell dyscrasia. Abnormalities detected by FISH analysis using an IGH@/CCND1 probe set were seen in 54% with RS, and 44% with column-based. We found a statistically significant difference between the yield of abnormalities detected in paired positive cases (p = 0.0001). An additional 183 consecutive post-validation samples sorted by RS showed recurrent genetic abnormalities in 85/120 (71%) of successfully sorted samples with ≥ 1% plasma cells but in none of 63 samples in which FISH analysis was completed on samples that could not be sorted due to insufficient plasma cells upon cell sorting. The column-free method successfully sorted PC, when present in ≥ 1% of cells, for detection of abnormalities by FISH. Furthermore, our data suggest that FISH analysis should not be performed on samples with an inadequate yield at the cell selection step.

Expression of CD19 and lack of miR-223 distinguish extramedullary plasmacytoma from multiple myeloma

AIMS

Extramedullary plasmacytoma (EMP) and multiple myeloma (MM) are both plasma cell (PC) tumours that are usually distinguished by clinical manifestations, but not by histopathological examination alone. However, EMP may express B-cell markers, such as CD79a and CD20, and MM may express germinal centre B-cell (GCBC)-associated microRNAs, such as miR-93 and miR-181b. Down-regulation of miR-30a or up-regulation of miR-223 is associated with the transition from GCBCs into PCs or memory B-cells, respectively. We studied B-cell markers and microRNAs to establish criteria that could distinguish EMP from MM.

METHODS AND RESULTS

Immunostains for the B-cell markers CD19, CD20, CD79a and PAX5 were performed. Expression levels of microRNAs 30a, 93, 181b and 223 were measured by real-time reverse transcription polymerase chain reactions. 73% of EMPs expressed CD19 whereas MM cases were negative. EMP and MM had similar levels of miR-30a, miR-93, and miR-181b, but EMP lacked expression of miR-223.

CONCLUSIONS

The presence of CD19 and lack of miR-223 suggested aberrant B-cell differentiation in EMP. Although the underlying mechanism for this differential expression was unclear, a CD19(+) /miR-223(-) phenotype could be used to distinguish EMP from the CD19(-) /miR-223(+) phenotype of MM.

Utility of flow cytometry immunophenotyping in multiple myeloma and other clonal plasma cell-related disorders

In recent years, multiparameter flow cytometry (MFC) immunophenotyping has become mandatory in the clinical management of hematological malignancies, both for diagnostic and monitoring purposes. Multiple myeloma (MM) and other clonal plasma cell-related (PC) disorders should be no exception to this paradigm, but incorporation of immunophenotypic studies in the management of patients with PC disorders is still far from being routinely established in many diagnostic flow cytometry laboratories. For clonal PC disorders, MFC is of clear and established clinical relevance in: (1) the differential diagnosis between MM and other PC-related disorders; (2) the identification of high-risk MGUS and smoldering MM; (3) minimal residual disease investigation after therapy; additionally it may also be useful for (4) the definition of prognosis-associated antigenic profiles; and (5) the identification of new therapeutic targets. In this article, we review the clinical value of MFC in the study of PC disorders, with specific emphasis in those areas where consensus exists on the need to incorporate MFC into routine evaluation of MM and other clonal PC-related disorders.

Flow cytometric immunophenotyping and minimal residual disease analysis in multiple myeloma

Presence of normal plasma cells (PCs), hemodilution of bone marrow aspirate, and changes in the immunophenotype are important considerations in minimal residual disease (MRD) assessment in multiple myeloma (MM). We evaluated 124 subjects-107 with MM, 11 with Hodgkin lymphoma, and 6 allogeneic stem cell transplantation donors-for the immunophenotype of neoplastic, reactive, and normal PCs respectively. Of the patients with MM, 36 were evaluated for MRD and 23 for a change in immunophenotype after chemotherapy. The immunophenotype of normal and reactive PCs was similar and differed from that of neoplastic PCs with respect to CD19, CD45, CD56, CD52, CD20, and CD117. At least 2 antigens were aberrantly expressed in all cases and 3 in 90.7% of MM cases. A change in the immunoprofile of PCs was observed in 18 (78%) of 23 cases. By using flow cytometry, we detected MRD in all samples, and a neoplastic PC index (percentage of neoplastic PCs/total bone marrow PCs) of less than 30 could differentiate immunofixation (IFx)- from IFx+ samples (complete and partial responders, respectively).

Utility of CD56 immunohistochemical studies in follow-up of plasma cell myeloma

Although 70% to 80% of plasma cell myelomas (PCMs) express CD56, few data are available on the usefulness of CD56 immunohistochemical analysis in assessing residual disease. We retrospectively reviewed 127 PCM posttreatment bone marrow (BM) specimens, classifying them as positive or negative for residual disease (independent of CD56 immunohistochemical studies) based on abnormal plasma cell (PC) morphologic features or flow cytometry (FC) and/or light chain restriction by immunohistochemical studies (conventional criteria). CD56 immunohistochemical analysis was performed on these and 20 negative lymphoma staging BM specimens. Of 127 BM specimens, 74 were positive and 53 were negative for residual PCM by conventional criteria. Of 74 BM specimens positive by conventional criteria, 59 (80%) demonstrated CD56 (strong+) PCs in clusters and/or with cytologic atypia. Of the 53 BM specimens negative by conventional criteria, 3 showed CD56 (strong+) morphologically atypical PCs in clusters or scattered. CD56 immunohistochemical analysis is useful for detecting residual PCM, particularly in morphologically equivocal cases in which light chain restriction cannot be demonstrated, and may serve as a potential response criterion.

Immunophenotypic studies of monoclonal gammopathy of undetermined significance

BACKGROUND

Monoclonal gammopathy of undetermined significance (MGUS) is a common plasma cell dyscrasia, comprising the most indolent form of monoclonal gammopathy. However, approximately 25% of MGUS cases ultimately progress to plasma cell myeloma (PCM) or related diseases. It is difficult to predict which subset of patients will transform. In this study, we examined the immunophenotypic differences of plasma cells in MGUS and PCM.

METHODS

Bone marrow specimens from 32 MGUS patients and 32 PCM patients were analyzed by 4-color flow cytometry, using cluster analysis of ungated data, for the expression of several markers, including CD10, CD19, CD20, CD38, CD45, CD56 and surface and intracellular immunoglobulin light chains.

RESULTS

All MGUS patients had two subpopulations of plasma cells, one with a "normal" phenotype [CD19(+), CD56(-), CD38(bright +)] and one with an aberrant phenotype [either CD19(-)/CD56(+) or CD19(-)/CD56(-)]. The normal subpopulation ranged from 4.4 to 86% (mean 27%) of total plasma cells. Only 20 of 32 PCM cases showed an identifiable normal subpopulation at significantly lower frequency [range 0-32%, mean 3.3%, p << 0.001]. The plasma cells in PCM were significantly less likely to express CD19 [1/32 (3.1%) vs. 13/29 (45%), p << 0.001] and more likely to express surface immunoglobulin [21/32 (66%) vs. 3/28 (11%), p << 0.001], compared to MGUS. Those expressing CD19 did so at a significantly lower level than in MGUS, with no overlap in mean fluorescence intensities [174 +/- 25 vs. 430 +/- 34, p << 0.001]. There were no significant differences in CD56 expression [23/32 (72%) vs. 18/29 (62%), p = 0.29], CD45 expression [15/32 (47%) vs. 20/30 (67%), p = 0.10] or CD38 mean fluorescence intensities [6552 +/- 451 vs. 6365 +/- 420, p = 0.38]. Two of the six MGUS cases (33%) with >90% CD19(-) plasma cells showed progression of disease, whereas none of the cases with >10% CD19(+) plasma cells evolved to PCM.

CONCLUSION

MGUS cases with potential for disease progression appeared to lack CD19 expression on >90% of their plasma cells, displaying an immunophenotypic profile similar to PCM plasma cells. A higher relative proportion of CD19(+) plasma cells in MGUS may be associated with a lower potential for disease progression.